Incoming Interface - HP 7102dl - ProCurve Secure Router Configuration Manual

Configuring Multicast Support with PIM-SM
Troubleshooting PIM-SM
13-52
Table 13-4. Flags in Typical Multicast Routing Table Entries
Flags Meaning
(*, G) entry The router is an edge router for this group.
SC
(*, G) entry Typically, the router is RP for this group.
SJ
(*, G) entry Typically, the router is RP for this group, and it also connects directly to hosts
that are members of this group.
SCJ
(S, G) entry The router is receiving and forwarding multicast traffic on an SP tree.
ST If the router is the DR for a directly connected source, the RP has already
joined the SP tree and the DR is no longer sends the register packets.
(S, G) entry The router is receiving multicast traffic on the SP tree, but this tree diverges
from the RP tree that the router was originally using.
SJR
One or more or all of the outgoing interfaces in the corresponding (*, G) entry
may be absent from this entry because neighbors are using different
connections in the SP tree.
(S, G) entry The router is DR for a directly connected source. It is currently registering
with the RP.
SFT

Incoming Interface

The router determines a multicast route's incoming interface and upstream
neighbor using RPF. For a (*, G) entry, the router looks up the best route to
the RP in its unicast routing table. For an (S, G) entry, the router looks up the
best route to the source. The router lists the forwarding interface indicated in
the best unicast route as the multicast route's incoming interface. The router
enters the next hop address of the unicast route for the address of the
multicast route's RPF neighbor. (See Figure 13-20 to learn how to find the
incoming interface and RPF neighbor for an entry.)
The incoming interface is very important for multicast routing with PIM-SM
because multicast traffic must follow a unidirectional flow. If a multicast
traffic does not arrive on the interface indicated in the matching entry, the
router discards it. Therefore, if an edge router has a null incoming interface
for an entry, it will not be able to receive multicast traffic for that entry.
A router should only have a (*, G) entry with a null incoming interface if it is
the RP for that group. The RP will receive a register packet from the DR as a
unicast, not as a multicast, so it will not discard it. The RP then will create a
(S, G) entry for which the incoming interface connects to the source address
for the encapsulated multicast.